The
first photographs of a new
and ominous crack in Greenland’s enormous Petermann
Glacier were captured by a NASA airborne mission Friday.

NASA’s
Operation IceBridge, which has been flying over northwest Greenland
for the past several days, took the photos after being provided
coordinates byStef
Lhermitte, a professor at Delft University of Technology in
the Netherlands, who had spotted the oddly located chasm by examining
satellite images.

The
NASA pictures make clear that a significant new rift has opened
near the center of the glacier’s floating ice shelf — an unusual
location that raises questions about how it formed. Moreover, this
crack is not so distant from another much wider and longer crack
that has been slowly extending toward the shelf’s center from its
eastern side wall. The two cracks are clearly visible in this image
taken from the aircraft:

Oblique
photo of a portion of the new rift, near bottom center, on Petermann
Glacier’s floating ice shelf and an older curved rift from the
flank of the shelf, near top center. The shaded feature near the
bottom center is a medial flow line, which may exert a stagnating
effect on the propagation of the new rift toward the older one.
(Kelly Brunt/NASA)

If
the two cracks were to intersect, then a single break would run
across more than half of the ice shelf. That might, in turn, cause
the piece to begin to break way.

But
in the image NASA also noted another feature in the ice that it
termed a “medial flow line” that, it said, “may exert a
stagnating effect on the propagation of the new rift toward the older
one.” So it remains to be seen just how much, and how rapidly, the
new rift — which has only just been discovered — could undermine
the floating ice self.

Still,
there’s good precedent for worrying about what could happen at
Petermann. When two prior ice islands broke off the glacier in 2010
and 2012 — the 2010 island in particular was extremely large —
the events drew major media attention and were even discussed in a
hearing before Congress.

“Last
week, an ice sheet covering 100 square miles broke off Greenland,”
then-Rep. Edward J. Markey (D-Mass.), the chairman of the Select
Committee on Energy Independence and Global Warming, said at
the opening of the hearing in summer 2010. “This giant ice island
is more than four times the size of Manhattan. It is the largest
piece of Arctic ice to break free in nearly half a century.”

Those
past breaks also caused the glacier’s floating ice shelf to become
much smaller than it had been before. Here’s a figure, courtesy of
Jason Box of the Geological Survey of Denmark and Greenland,
capturing the glacier’s shrinkage:

(Jason
Box)

Petermann
Glacier has grown back somewhat since those breaks because of
its steady flow outward (at a rate that appears to be accelerating
somewhat). But if the next piece breaks off, the red line in the
graph above would plunge once again. Box estimated the resulting ice
island would be some 50 to 70 square miles in size, or more than
twice the size of Manhattan.

NASA’s Operation
IceBridge is a research mission in which instrumented
aircraft are flown over ice at both poles — both Greenland and
Antarctica — to collect data about the state of polar ice and how
it is changing. IceBridge operates over Greenland at this time of
year and snapped the photos on what appeared to be a crystal-clear
day at the glacier.

It
has also taken recent photos of other nearby glaciers, such as
Heilprin and Upernavik, and the state of floating sea ice in the
channel between northwestern Greenland and northeastern Canada, in
addition to its extensive data-gathering work.

After
seeing the new NASA images, Lhermitte responded that it was “amazing
to see the rift from nearby after studying it from space for several
days.” But, he added, “From these images alone, it is difficult
to already say anything about what exactly caused the crack on this
unusual spot.”

The
crack appeared in the middle of the floating shelf, rather than on
one of its sides, as is typical of this glacier — leading Lhermitte
to wonder whether it could have been caused by the ocean waters below
the self.

You
can bet that scientists will be conducting a great deal more research
on this crack, what caused it and whether it might precipitate bigger
changes to Petermann Glacier.